Method for preparing polarizing plate locally having depolarization region, and polarizing plate prepared by using same

ABSTRACT

The present invention relates to a method for manufacturing a polarizing plate, the method including: preparing a polarizing plate where a protection film is laminated on one surface of a polyvinyl alcohol-based polarizer dyed with at least one or more of iodine and dichromatic dyes; and forming a depolarization region having single transmittance of 80% or more at a wavelength band in a range of 400 nm to 800 nm by bringing a decoloring solution including 1 to 30 wt % of a decolorant into local contact with the other surface of the polarizer, and a polarizing plate manufactured by using the same.

TECHNICAL FIELD

This application claims priority to and the benefit of Korean PatentApplication Nos. 10-2014-0129209 and 10-2014-0080490 filed in the KoreanIntellectual Property Office on Sep. 26, 2014 and Jun. 30, 2014,respectively, the entire contents of which are incorporated herein byreference.

The present invention relates to a method for manufacturing a polarizingplate, and a polarizing plate manufactured by using the same, and moreparticularly, to a polarizing plate locally having a depolarizationregion to be suitable for equipment of parts such as camera modules andcolor formation, and a method for manufacturing the same.

BACKGROUND ART

A polarizing plate is applied to various display devices such as aliquid crystal display and an organic electroluminescent device.Recently, the mainly used polarizing plate is in a form where aprotection film is laminated on one surface or both surfaces of a PVApolarizer manufactured by alignment by a method for dyeing iodine and/ordichromatic dyes on a polyvinyl alcohol (hereinafter, PVA)-based film,and then cross-linking the iodine and/or dichromatic dyes by using boricacid and the like, followed by elongation.

Meanwhile, there is a current trend toward increasing slimness of thedisplay device, and in order to implement a large screen, the displaydevice has been developed toward a trend where thicknesses of a bezelportion and an edge where the screen is not displayed are minimized.Further, in order to implement various functions, parts such as camerastend to be equipped in a display device, and in consideration of adesign factor, efforts of providing various colors to a product logo oran edge region or decoloring the product logo or the edge region havebeen made.

However, in the case of a polarizing plate in the related art, since anentire region of the polarizing plate is dyed with iodine and/ordichromatic dyes, the polarizing plate has a dark black color, and as aresult, there are problems in that it is difficult to provide variouscolors to a display device, and particularly, in the case where thepolarizing plate is positioned on parts such as cameras, 50% or more ofthe quantity of light is absorbed by the polarizing plate to reducevisibility of a camera lens.

In order to solve the problems, a method for physically removing aportion of the polarizing plate, which covers the camera lens, bypiercing a hole (boring) in the portion of the polarizing plate by amethod such as punching and cutting has been commercialized.

However, the aforementioned physical method degrades an appearance ofthe image display, and the polarizing plate may be damaged due tocharacteristics of a process of piercing the hole. Meanwhile, in orderto prevent damage such as tearing of the polarizing plate, a boredportion of the polarizing plate should be formed in a regionsufficiently far away from a corner, and as a result, there is a problemin that in the case when the polarizing plate is applied, the bezelportion of the image display is relatively widened which deviates from acurrent narrow bezel design trend of the image display. Further, thereis a problem in that in the case where a camera module is equipped inthe bored portion of the polarizing plate, as described above, since thecamera lens is exposed to the outside, the camera lens is easilycontaminated and damaged when the camera lens is used over a long periodof time.

Therefore, in order to overcome the aforementioned problems, adevelopment of a new process of providing a method for decoloring alocal region of a polarizer without boring to form a depolarizationregion, and simultaneously, suppressing fine wrinkles and surfaceroughness that may occur in the depolarization region to reduce a hazeis needed.

DETAILED DESCRIPTION OF THE INVENTION Technical Problem

The present invention has been made in an effort to solve theaforementioned problems, to provide a polarizing plate wherepolarization of some regions of the polarizing plate is removed and amethod for manufacturing the same, and to provide a polarizing platewhere surface roughness and a haze are excellent by removingpolarization while a hole is not physically pierced like the relatedart, and simultaneously, minimizing wrinkles of the region from whichpolarization is removed.

Technical Solution

According to an exemplary embodiment of the present invention, thepresent invention provides a method for manufacturing a polarizingplate, the method including: preparing a polarizing plate where aprotection film is laminated on one surface of a polyvinyl alcohol-basedpolarizer dyed with at least one or more of iodine and dichromatic dyes;and forming at least one depolarization region having singletransmittance of 80% or more at a wavelength band in a range of 400 nmto 800 nm by bringing a decoloring solution including 1 to 30 wt % of adecolorant into local contact with the other surface of the polarizer.

Further, it is preferable that the decolorant includes one kind or moreselected from the group consisting of sodium hydroxide (NaOH), sodiumhydrosulfide (NaSH), sodium azide (NaN₃), potassium hydroxide (KOH),potassium hydrosulfide (KSH), and potassium thiosulfate (KS₂O₃).

It is preferable that a pH of the decoloring solution is 11 to 14 and aviscosity of the decoloring solution be 1 cP to 2000 cP.

Meanwhile, it is preferable that the decoloring solution furtherincludes a viscosity agent, and it is preferable that the viscosityagent includes one kind or more selected from the group consisting of apolyvinyl alcohol-based resin, a polyvinyl acetoacetate-based resin, anacetoacetyl group-denatured polyvinyl alcohol-based resin,butenediolvinyl alcohols, a polyethylene glycol-based resin, and apolyacrylamide-based resin.

In this case, it is preferable that the method further includes, afterthe forming of the depolarization region, performing washing by usingalcohol or an acid solution.

Further, the manufacturing method of the present invention may furtherinclude, if necessary, after the forming of at least one depolarizationregion, forming an optical layer on at least one surface of thepolarizing plate.

Further, the method may further include, after the forming of thedepolarization region, forming an optical layer on at least one surfaceof the polarizing plate, and the optical layer may be a protection film,a retardation film, a luminance improvement film, a hard coating layer,an antireflection layer, a cohesive layer, an adhesion layer, or acombination thereof.

Further, the present invention provides a polarizing plate manufacturedby the aforementioned manufacturing method, the polarizing plateincluding: a polyvinyl alcohol-based polarizer dyed with at least one ormore of iodine and dichromatic dyes, and a protection film laminated onat least one surface of the polyvinyl alcohol-based polarizer, in whichthe polarizing plate locally has a depolarization region having singletransmittance of 80% or more at a wavelength band in a range of 400 nmto 800 nm, and arithmetic mean roughness (Ra) of the depolarizationregion is 100 nm or less.

Further, it is preferable that root mean square roughness (Rq) of thedepolarization region is 100 nm or less.

In this case, in the depolarization region of the polarizer, thepolarization degree may be 20% or less, and in a region other than thedepolarization region, single transmittance may be 40% to 45% and thepolarization degree may be 99% or more.

Further, it is preferable that in the depolarization region of thepolarizing plate, a haze is 3% or less.

In this case, it is preferable that in the depolarization region, acontent of at least one or more of the iodine and dichromatic dyes is0.1 wt % to 0.5 wt %, and in a region other than the depolarizationregion, the content of at least one or more of the iodine anddichromatic dyes is 1 wt % to 4 wt %.

The area of the depolarization region according to the aforementionedmanufacturing method and the area of the depolarization region accordingto the aforementioned polarizing plate may be 0.5 mm² or more and 500mm² or less.

Advantageous Effects

The present invention can minimize damage such as holes or tearing of apolarizing plate by bringing a decoloring solution into contact withsome regions of a polyvinyl alcohol-based polarizer to depolarize thecorresponding region. In the case where the polarizing plate of thepresent invention manufactured by the aforementioned method is used,even though the polarizing plate is equipped on parts such as cameras, aproblem caused by a reduction in luminance does not occur.

Further, in the manufacturing method of the present invention, first,after a protection film is laminated on one surface of the polarizer,decoloring is performed, and thus it is possible to provide thepolarizing plate where surface roughness and a haze of thedepolarization region are excellent by suppressing a phenomenon wherethe polarizer absorbs moisture to be swollen in a decoloring process andthus minimizing fine wrinkles.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a 3D picture obtained by photographing a surface of adepolarization region in a polarizing plate of Example 1 by using awhite light three dimension measuring machine (optical profiler).

FIG. 2 is a 3D picture obtained by photographing a surface of adepolarization region in a polarizer of Comparative Example 1 by using awhite light three dimension measuring machine (optical profiler).

BEST MODE

Hereinafter, preferred exemplary embodiments of the present inventionwill be described. However, exemplary embodiments of the presentinvention can be modified into various other forms, and the scope of thepresent invention is not limited to the exemplary embodiments as will bedescribed below. Further, the exemplary embodiments of the presentinvention are provided so that those skilled in the art may morecompletely understand the present invention.

The present inventors found that in the case where a decoloring solutioncomes into selective contact with some regions of a polyvinylalcohol-based polarizer dyed with iodine and/or dichromatic dyes tolocally form a depolarization region, unlike a physical removing methodsuch as punching and cutting, boring was not formed, and fine wrinklesof the depolarization region can be minimized by laminating a protectionfilm on one surface of the polarizer and then performing a decoloringprocess to suppress a swelling phenomenon of the polarizer, therebyaccomplishing the present invention.

A method for manufacturing a polarizing plate according to the presentinvention includes step i) of preparing the polarizing plate where aprotection film is laminated on one surface of a polyvinyl alcohol-basedpolarizer dyed with at least one or more of iodine and dichromatic dyes;and step ii) of forming a depolarization region having singletransmittance of 80% or more at a wavelength band in a range of 400 nmto 800 nm by bringing a decoloring solution including 1 to 30 wt % of adecolorant into local contact with the other surface of the polarizer.

In the present specification, “single transmittance” is represented byan average value of transmittance of an absorption axis andtransmittance of a transmission axis of the polarizing plate. Further,“single transmittance” and “the polarization degree” of the presentspecification are values measured by using the V-7100 model manufacturedby JASCO company.

Generally, in the case where the decoloring solution comes into directcontact with the polyvinyl alcohol-based polarizer on which theprotection film is not laminated, the swelling phenomenon of thepolarizer occurs due to moisture, and thus the wrinkles may be formed inthe depolarization region and a surrounding region thereof. In thiscase, surface roughness of the depolarization region is increased toincrease a haze, and thus it may be difficult to sufficiently secure anappearance of the polarizing plate and camera visibility. However, likethe present invention, in the case where before contact of thedecolorant, the protection film is laminated on one surface of thepolarizer, since the protection film and the polarizer are adhered toeach other, the occurrence of the swelling phenomenon and the wrinklesmay be suppressed.

Hereinafter, each step of the manufacturing method of the presentinvention will be more specifically described.

First, step i) of preparing the polarizing plate where the protectionfilm is laminated on one surface of the polyvinyl alcohol-basedpolarizer dyed with at least one or more of the iodine and dichromaticdyes may be performed through a method for manufacturing a polarizingplate, which is well known in the corresponding technical field, or maybe performed by a method of purchasing a polarizing plate commerciallyavailable on the market, in which a protection film is laminated on onesurface of a polarizer.

Meanwhile, as an example of the method for manufacturing the polarizingplate, it is possible to use the method including: a step of preparingthe polyvinyl alcohol-based polarizer dyed with the iodine and/ordichromatic dyes; and a step of laminating the protection film on onesurface of the polarizer. For example, the step of preparing thepolyvinyl alcohol-based polarizer may be performed through a dyeing stepof dyeing a polyvinyl alcohol-based polymer film with the iodine and/ordichromatic dyes, a cross-linking step of cross-linking the polyvinylalcohol-based film and the dye, and an elongation step of elongating thepolyvinyl alcohol-based film, but the step is not limited thereto.

First, the dyeing step is configured to dye the iodine molecules and/ordichromatic dyes on the polyvinyl alcohol-based film, and the iodinemolecules and/or dichromatic dye molecules may absorb light thatvibrates in an elongation direction of the polarizer and allow lightthat vibrates in a vertical direction to pass, thus obtainingpolarization having a predetermined vibration direction. In this case,the dyeing may be, for example, performed by impregnating the polyvinylalcohol-based film in a treatment bath including an iodine solutionand/or a solution containing the dichromatic dye.

In this case, as a solvent used in the solution of the dyeing step,water is generally used, but an organic solvent having compatibilitywith water may be added in an appropriate amount. Meanwhile, the iodineand/or dichromatic dyes may be used in a content of 0.06 parts by weightto 0.25 parts by weight based on 100 parts by weight of the solvent. Thereason is that in the case where the content of the dichromatic materialsuch as iodine is in the aforementioned range, transmittance of thepolarizer manufactured after elongation may satisfy the range of 40.0%to 47.0%.

Meanwhile, in the case where iodine is used as the dichromatic material,in order to improve dyeing efficiency, it is preferable that asupplement agent such as an iodide compound is further contained, andthe supplement agent may be used at a ratio of 0.3 parts by weight to2.5 parts by weight based on 100 parts by weight of the solvent. In thiscase, the supplement agent such as the iodide compound is added in orderto increase solubility of iodine to water because solubility of iodineto water is low. Meanwhile, it is preferable that a mixing ratio ofiodine and the iodide compound is 1:5 to 1:10 on the basis of a weight.

In this case, specific examples of the iodide compound that may be addedin the present invention may include potassium iodide, lithium iodide,zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide,calcium iodide, tin iodide, titanium iodide, a mixture thereof, or thelike, but are not limited thereto.

Meanwhile, it is preferable that a temperature of the treatment bath ismaintained at 25° C. to 40° C. In the case where the temperature of thetreatment bath is less than 25° C., which is low, dyeing efficiency maybe reduced, and much sublimation of iodine may occur at a very hightemperature that is more than 40° C. to increase a use amount of iodine.

In this case, it is preferable that an immersion time of the polyvinylalcohol-based film in the treatment bath is 30 seconds to 120 seconds.This is because in the case where the immersion time is less than 30seconds, dyeing may not be uniformly performed on the polyvinylalcohol-based film, and in the case where the immersion time is morethan 120 seconds, dyeing is saturated, and thus immersion is not neededany longer.

Meanwhile, the cross-linking step is configured to adsorb the iodineand/or dichromatic dyes on a polyvinyl alcohol polymer matrix, and adeposition method for performing the cross-linking step by depositingthe polyvinyl alcohol-based film in a cross-linking bath including aboric acid aqueous solution and the like is generally used, but themethod is not limited thereto, and the cross-linking step may beperformed by an application method or spray method for applying orspraying a solution including a cross-linking agent on the polyvinylalcohol-based film.

In this case, as a solvent used in the solution of the cross-linkingbath, water is generally used, but an organic solvent havingcompatibility with water may be added in an appropriate amount, and thecross-linking agent may be added in an amount of 0.5 parts by weight to5.0 parts by weight based on 100 parts by weight of the solvent. In thiscase, in the case where the cross-linking agent is contained in theamount of less than 0.5 parts by weight, cross-linking is insufficientin the polyvinyl alcohol-based film, and thus strength of the polyvinylalcohol-based film in water may be reduced, and in the case where theamount is more than 5.0 parts by weight, excessive cross-linking isformed, and thus an elongation property of the polyvinyl alcohol-basedfilm may deteriorate. Further, specific examples of the cross-linkingagent may include a boron compound such as a boric acid and borax,glyoxal, glutaraldehyde, and the like, and may be used alone or may beused in combination.

Meanwhile, a temperature of the cross-linking bath depends on the amountand an elongation ratio of the cross-linking agent and is not limitedthereto, but, generally, it is preferable that the temperature is 45° C.to 60° C. Generally, if the amount of the cross-linking agent isincreased, in order to improve mobility of chains of the polyvinylalcohol-based film, the temperature of the cross-linking bath isadjusted to a high temperature condition, and if the amount of thecross-linking agent is small, the temperature of the cross-linking bathis adjusted to a relatively low temperature condition. However, sincethe present invention is a process of performing five times or moreelongation, in order to improve the elongation property of the polyvinylalcohol-based film, the temperature of the cross-linking bath should bemaintained at 45° C. or more. Meanwhile, it is preferable that theimmersion time of the polyvinyl alcohol-based film in the cross-linkingbath is 30 seconds to 120 seconds. The reason is that in the case wherethe immersion time is less than 30 seconds, cross-linking may not beuniformly performed on the polyvinyl alcohol-based film, and in the casewhere the immersion time is more than 120 seconds, cross-linking issaturated, and thus immersion is not needed any longer.

Meanwhile, elongation in the elongation step is configured to alignpolymer chains of the polyvinyl alcohol-based film in a predetermineddirection, and an elongation method may be classified into a wetelongation method and a dry elongation method, the dry elongation methodis classified into an inter-roll elongation method, a heating rollelongation method, a compression elongation method, a tenter elongationmethod, and the like, and the wet elongation method is classified into atenter elongation method, an inter-roll elongation method, and the like.

In this case, it is preferable that in the elongation step, thepolyvinyl alcohol-based film is elongated at an elongation ratio of 4times to 10 times. The reason is that the polymer chains of thepolyvinyl alcohol-based film should be aligned in order to providepolarization performance to the polyvinyl alcohol-based film, and thechains may not be sufficiently aligned at the elongation ratio of lessthan 4 times, and the chains of the polyvinyl alcohol-based film may becut at the elongation ratio of more than 10 times.

In this case, it is preferable that the elongation is performed at anelongation temperature of 45° C. to 60° C. This is because theelongation temperature may depend on the content of the cross-linkingagent, mobility of the chains of the polyvinyl alcohol-based film may bereduced at the temperature of less than 45° C. to reduce elongationefficiency, and in the case where the temperature is more than 60° C.,the polyvinyl alcohol-based film may be softened to weaken strength.Meanwhile, the elongation step may be performed simultaneously with thedyeing step or the cross-linking step or separately from the dyeing stepor the cross-linking step.

Meanwhile, the elongation may be performed with only the polyvinylalcohol-based film, or may be performed by a method of laminating a basefilm on the polyvinyl alcohol-based film and then elongating thepolyvinyl alcohol-based film and the base film together. In the lattermethod, in the case where the polyvinyl alcohol-based film having asmall thickness (for example, PVA film of 60 μm or less) is elongated,in the elongation process, elongation may be used in order to preventthe polyvinyl alcohol-based film from being broken, and may be used inorder to manufacture a thin PVA polarizer of 10 μm or less.

In this case, as the base film, polymer films having a maximumelongation magnification of 5 times or more under a temperaturecondition of 20° C. to 85° C. may be used, and for example, a highdensity polyethylene film, a polyurethane film, a polypropylene film, apolyolefin film, an ester-based film, a low density polyethylene film,high density polyethylene and low density polyethylene co-extrusionfilms, a copolymer resin film in which ethylene vinyl acetate iscontained in high density polyethylene, an acryl film, a polyethyleneterephthalate film, a polyvinyl alcohol-based film, a cellulose-basedfilm, and the like may be used. Meanwhile, the maximum elongationmagnification means an elongation magnification immediately beforebreakage occurs.

Further, a lamination method of the base film and the polyvinylalcohol-based film is not particularly limited. For example, the basefilm and the polyvinyl alcohol-based film may be laminated via anadhesive or a cohesive agent, or may be laminated by a mode where thepolyvinyl alcohol-based film is set on the base film without a separatemedium. Further, lamination may be performed by a method of co-extrudinga resin forming the base film and a resin forming the polyvinylalcohol-based film, or may be performed by a method of applying apolyvinyl alcohol-based resin on the base film. Meanwhile, the base filmmay be detached from the polarizer and removed after elongation iscompleted, but may not be removed but be subjected to a next step. Inthis case, the base film may be used as a polarizer protection filmwhich will be described below and the like.

Next, in the present invention, if the polyvinyl alcohol-based polarizeris prepared through the aforementioned method, the step of laminatingthe protection film on one surface of the polyvinyl alcohol-basedpolarizer is performed.

In this case, the protection film is a film for protecting the polarizerhaving a very small thickness, and refers to a transparent film attachedonto one surface of the polarizer, and a film having excellentmechanical strength, thermal stability, moisture blocking property, andisotropicity may be used. For example, an acetate-based resin film suchas triacetyl cellulose (TAC), and polyester-based,polyethersulfone-based, polycarbonate-based, polyamide-based,polyimide-based, polyolefin-based, cycloolefin-based,polyurethane-based, and acryl-based resin films, and the like may beused, but the protection film is not limited thereto.

Further, the protection film may be an isotropic film or an anisotropicfilm to which an optical compensation function such as retardation isprovided, and the protection film may be constituted as one film or maybe constituted by attaching two films or more. Further, the protectionfilm may be a non-elongated film or a uniaxially or biaxially elongatedfilm, and a thickness of the protection film may be generally 1 μm to500 μm and preferably 1 μm to 300 μm.

In this case, adhesion force of the protection film to the polyvinylalcohol-based polarizer may be preferably 1 N/2 cm or more and morepreferably 2 N/2 cm or more. Specifically, the aforementioned adhesionforce means adhesion force measured by 900 stripping force by using atexture analyzer after the protection film is attached onto thepolyvinyl alcohol-based polarizer dyed with at least one or more of theiodine and dichromatic dyes. In the case where the adhesion forcesatisfies the aforementioned range, swelling of the protection film andthe polyvinyl alcohol-based polarizer may be suppressed, and in amanufacturing process, the occurrence of curls and defects may beminimized.

Meanwhile, in the step of laminating the protection film on one surfaceof the polyvinyl alcohol-based polarizer, the protection film isattached onto the polarizer, and attachment may be performed by using anadhesive. In this case, attachment may be performed through a laminationmethod of films well known in the corresponding technical field, and forexample, attachment may be performed by using an adhesive well known inthe corresponding technical field, such as a water-based adhesive suchas a polyvinyl alcohol-based adhesive, a thermosetting adhesive such asa urethane-based adhesive, a light cation curable adhesive such as anepoxy-based adhesive, and a light radical curable adhesive such as anacryl-based adhesive.

Next, in the present invention, as described above, after the polarizingplate where the protection film is laminated on one surface of thepolyvinyl alcohol-based polarizer is prepared, step ii) of forming thedepolarization region having single transmittance of 80% or more at thewavelength band in a range of 400 nm to 800 nm by bringing thedecoloring solution including 1 to 30 wt % of the decolorant into localcontact with the other surface of the polarizer is performed.

In this case, the other surface of the polarizer refers to an oppositesurface where the protection film is not laminated, in the polarizer ofstep i) on which the protection film is laminated on one surfacethereof. That is, since the decoloring solution should come into directcontact with the polyvinyl alcohol-based polarizer, not the protectionfilm, the present step should be performed over the other surface of thepolarizer.

Meanwhile, the decoloring solution essentially includes a decolorant,which may decolor the iodine and/or dichromatic dyes, and a solvent. Thedecolorant is not particularly limited as long as the decolorant candecolor the iodine and/or dichromatic dyes dyed on the polarizer, but,for example, it is preferable that the decolorant includes one kind ormore selected from the group consisting of sodium hydroxide (NaOH),sodium hydrosulfide (NaSH), sodium azide (NaN₃), potassium hydroxide(KOH), potassium hydrosulfide (KSH), and potassium thiosulfate (KS₂O₃).

As the solvent, it is preferable that water such as distilled water isused. Further, the solvent may be used while being additionally mixedwith an alcohol-based solvent. For example, the solvent may be usedwhile being mixed with methanol, ethanol, butanol, isopropyl alcohol, orthe like, but the solvent is not limited thereto.

Meanwhile, the content of the decolorant in the decoloring solution maybe changed according to a contact time in a decoloring process, but thedecolorant may be included in the content of preferably 1 wt % to 30 wt% and more preferably 5 wt % to 15 wt %, based on the total weight ofthe decoloring solution. In the case where the content of the decolorantis less than 1 wt %, decoloring is not performed or decoloring isperformed for a time of decades minutes or more, and thus it isdifficult to substantially apply the decolorant, and in the case wherethe content thereof is more than 30 wt %, since the decoloring solutionis not easily diffused into the polarizer, an increment in decoloringefficiency is insignificant, and thus economic feasibility is reduced.

Further, the pH of the decoloring solution is 11 to 14 and morepreferably 13 to 14. The decolorant of the present invention is a strongbasic compound and should have a strong basic property enough to breakboric acid forming a cross-linking bond with polyvinyl alcohol, and inthe case where the pH satisfies the aforementioned range, decoloring mayoccur well. For example, as a solution decomposing (decoloring) iodineto secure transparency (iodine clock reaction), sodium thiosulfate (pH7) may cause decoloring in a general iodine compound aqueous solutionbut does not cause decoloring in an actual polarizer (PVA) even thoughcontact is performed over a long period of time (10 hours). That is,this refers to that the cross-linking bond of the boric acid needs to bebroken due to the strong base before iodine is decomposed.

Meanwhile, in the present invention, the step of forming thedepolarization region by bringing the decoloring solution into contactwith the polarizer may be performed by using a printing device and thelike, and in this case, the step may be performed by a non-contact typeprinting method where the decolorant is applied on a desired localportion or in a pattern having a desired shape by using a dispenser orinkjet, or a contact type printing method such as gravure printing, butthe printing device is not limited thereto.

To be more specific, in consideration of easiness of performing acontinuous process, it is preferable that the aforementioned device is adevice performing printing by an inkjet marking method, a gravureprinting method, or the like. In this case, the inkjet marking methodrefers to a printing method performed in a mode where ink liquid dropsare dripped on a target (PVA polarizer) to be printed through an inkjetnozzle, and the gravure printing method refers to a printing methodperformed in a mode where ink is filled in a printing roll on which ashape to be printed is engraved, ink of a region other than the engravedportion is removed through a doctor blade and the like to allow ink toremain in only the engraved portion, and the ink filled in the engravedportion is then transferred onto a target (PVA polarizer) to be printedby using a transferring roll.

Further, in the present specification, the step of forming thedepolarization region by bringing the decoloring solution into contactwith the polarizer may be performed by using an immersion method.Specifically, in the immersion method, after a mask layer is formed onone surface of the polarizer, the polarizer including the protectionfilm and the release film may be immersed in the decoloring solution.

According to the exemplary embodiment of the present specification, themethod may further include, before the step of forming thedepolarization region, forming a mask layer including at least one ormore bored portions on the other surface of the polarizer. In this case,the mask layer may be formed of a mask film or a coating layer.

According to the exemplary embodiment of the present specification, thestep of forming the mask layer may be performed before the step ofproviding the protection film and the release film.

There are merits in that in the case where before the step of formingthe depolarization region, the step of forming the mask layer isperformed, since a portion not requiring depolarization, that is, aportion not requiring decoloring is not covered by the mask layer, adefect occurrence ratio in a roll-to-roll process may be reduced, andsince the polyvinyl alcohol-based polarizer and the mask layer arelaminated, a process speed is not limited.

If the polarizer where the mask layer including the bored portion isformed is immersed in the decoloring solution, the decoloring solutioncomes into contact with the polyvinyl alcohol-based polarizer throughthe bored portion, and as a result, decoloring partially occurs in onlya portion corresponding to a bored portion region.

According to another exemplary embodiment, in the case where the maskfilm is used as the mask layer, the step of forming the mask layer mayinclude: forming the bored portion in the mask film; and attaching themask film onto the other surface of the polarizer.

Specifically, in the step of forming the mask layer, the bored portionmay be formed in at least one region of the mask film, and the mask filmmay be attached onto the other surface of the polarizer. Further, in thestep of forming the mask layer, a coating layer may be formed on theother surface of the polarizer, and at least one region of the coatinglayer may be selectively removed to form the bored portion.

In this case, as the mask film, an olefin-based film such aspolyethylene (PE), polypropylene (PP), and polyethylene terephthalate(PET); or a vinyl acetate-based film such as ethylene vinyl acetate(EVA) and polyvinyl acetate may be used, but the mask film is notlimited thereto. Further, the thickness of the mask film may be 10 μm to100 μm and preferably 10 μm to 70 μm, but is not limited thereto.

The step of forming the bored portion in the mask film is notparticularly limited, and may be performed through film boring methodswell known in the corresponding technical field, for example, dieprocessing, knife processing, laser processing, and the like.

According to the exemplary embodiment of the present specification, thestep of forming the bored portion may be performed through laserprocessing. The laser processing may be performed by using laserprocessing devices generally known in the corresponding technical field,but is not particularly limited. Laser processing conditions such as akind, power, and a laser pulse repetition rate of the laser device maybe changed according to a material or a thickness of the film, a shapeof the bored portion, and the like, and in consideration of theaforementioned matters, a person with ordinary skill in the art mayappropriately select the laser process conditions. For example, in thecase where the polyolefin film having a thickness of 30 μm to 100 μm isused as the mask film, the bore portion may be formed by using a carbondioxide (CO₂) laser device having a central wavelength of about 9 μm to11 μm, a UV device having a central wavelength of about 300 nm to 400nm, or the like, and in this case, maximum average power of the laserdevice may be about 0.1 W to 30 W and the pulse repetition rate thereofmay be about 0 kHz to 50 kHz, but the laser device is not limitedthereto.

The step of forming the bored portion may be performed before or afterthe step of attaching the mask film onto the other surface of thepolarizer. In other words, the bored portion may be previously formed inthe mask film and the mask film where the bored portion is formed may bethen attached onto the polarizer, or the mask film may be attached ontothe polarizer and the bored portion may be then formed.

The step of attaching the mask film onto the other surface of thepolarizer may be performed by film lamination methods well known in thecorresponding technical field, for example, a method for attaching themask film and a polarizing member through a cohesive layer, and in thiscase, the cohesive layer may be formed by applying a cohesive agent,such as an acryl-based cohesive agent, a silicon-based cohesive agent,an epoxy-based cohesive agent, and a rubber-based cohesive agent, on themask film or the polarizing member, but the method and the cohesiveagent are not limited thereto. For example, in the case where filmshaving self-cohesive force (for example, EVA film, PVAC film, PP film,and the like) are used as the mask film, the mask film may be directlyattached onto the other surface of the polarizer while the cohesivelayer is not formed.

According to the exemplary embodiment of the present specification, inthe case where the mask layer is formed by the coating layer, the stepof forming the mask layer includes: forming the coating layer on theother surface of the polarizer; and forming the bored portion byselectively removing some regions of the coating layer.

The step of forming the coating layer may be performed by a method forapplying a composition for forming the coating layer on the othersurface of the polarizer, and then performing drying or irradiating heator an active energy beam such as a UV beam or an electron beam to curethe coating layer.

A kind of the composition for forming the coating layer is notparticularly limited as long as the composition may be etched by a laserand is not dissolved in an alkaline solution. For example, as thecomposition for forming the coating layer, a composition including adispersible polymer resin such as water-dispersible polyurethane,water-dispersible polyester, and a water-dispersible acryl copolymer, ora photosensitive resin composition may be used. Meanwhile, as thephotosensitive resin composition, photosensitive resin compositions thatare available on the market, for example, a positive type photoresist, anegative type photoresist, or the like may be used, but thephotosensitive resin composition is not particularly limited.

According to the exemplary embodiment of the present specification, thecoating layer may be formed by using the polymer resin composition orthe photosensitive resin composition.

A method for applying the composition for forming the coating layer isnot particularly limited, and application may be performed through anapplication method generally used in the corresponding technical field,for example, bar coating, spin coating, roll coating, knife coating,spray coating, or the like, and the curing may be performed by a methodfor applying heat or irradiating the active energy beam, such as theultraviolet beam or the electron beam, on the applied resin composition.

According to the exemplary embodiment of the present specification, athickness of the coating layer may be 100 nm to 500 nm. There are meritsin that in the case where the thickness of the coating layer satisfiesthe aforementioned numerical range, when the bored portion is processed,the polyvinyl alcohol-based polarizer may be prevented from beingdamaged, and a process of removing the coating layer after thedecoloring process need not be additionally performed.

The step of forming the bored portion by selectively removing someregions of the coating layer may be performed by a method forirradiating the energy beam on some regions of the coating layer,followed by vaporization, a photolithography method, or the like.

The method for vaporizing some of the coating layer may be performed byusing devices generally known in the corresponding technical field, forexample, a UV laser device having a central wavelength of 300 nm to 400nm, an IR laser device having a central wavelength of 1000 nm to 1100nm, a green laser device having a central wavelength of 500 nm to 550nm, or the like. Meanwhile, laser processing conditions such as a kind,laser power, and a pulse repetition ratio of the used laser device maybe changed according to a kind and a thickness of the coating layer,formation of the bored portion to be formed, and the like, and inconsideration of the aforementioned matters, a person with ordinaryskill in the art may appropriately select the laser process conditions.

According to the exemplary embodiment of the present specification, thestep of forming the bored portion by selectively removing some regionsof the coating layer may be performed through laser processing.

Meanwhile, in the case where the coating layer is formed of thephotosensitive resin composition, the bored portion may be formedthrough a photolithography process, and for example, the bored portionmay be formed by a method for applying the photosensitive resincomposition on the other surface of the polarizing plate, andselectively exposing the energy beam of a region corresponding to thebored portion, followed by developing by using a developing solution.

In this case, the exposure may be performed by using a light source suchas an ultraviolet beam or an energy beam such as a laser. There aremerits in that in the case where exposure is performed by using thelaser, a separate mask may not be used for exposure, and a shape of thebored portion may be relatively freely formed.

To be more specific, in the exemplary embodiment of the presentspecification, in the case where the coating layer is formed in athickness of 200 nm by using a photosensitive resin material, exposuremay be performed by using a core having maximum average power of 0.1 Wto 10 W and a UV laser of 300 nm to 400 nm, and in this case, an actionpulse repetition rate of the laser may be 30 kHz to 100 kHz.

Meanwhile, in the developing, an appropriate developing solution may beselected to be used according to a kind of the used photosensitiveresin, and in some cases, the aforementioned decoloring solution may beused as the developing solution. In this case, a separate developingstep may not be performed.

Meanwhile, the bored portion may be formed to correspond to a shape of aregion to be decolored, and a shape or a formation position thereof isnot particularly limited. For example, the bored portion may be formedat a position at which parts such as a camera are equipped, so as tocorrespond to a shape of the parts, or may be formed in a region inwhich a product logo is printed in a shape of the product logo, or inthe case where a color is provided to an edge portion of the polarizer,the bored portion may be formed at the edge portion of the polarizer tohave a frame shape.

According to the exemplary embodiment of the present specification,after the step of forming the depolarization region, if necessary, astep of removing a mask layer may be further included. The step ofremoving the mask layer may be performed by a method for stripping themask layer from the polarizer. In the case where the mask film is usedas the mask layer, it is preferable to perform the present step, but inthe case where the coating layer is used as the mask layer, the presentstep may not be performed. To be more specific, the step of removing themask layer may be performed by a method for stripping the mask layerfrom the polarizer by using a stripping roll and the like.

Meanwhile, the viscosity of the decoloring solution may be 1 cP to 2000cP and preferably 5 cP to 2000 cP. This is because in the case where theviscosity of the decoloring solution satisfies the aforementionednumerical range, a printing process may be smoothly performed, anddiffusion or flowing down into the printed decoloring solution accordingto movement of the polarizing member in a continuous process line may beprevented, and thus the decoloring region may be formed in a desiredshape in a desired region. Meanwhile, the viscosity of the decoloringsolution may be appropriately changed according to surface properties ofthe used printing device and polarizer and the like. For example, in thecase where the gravure printing method is used, the viscosity of thedecoloring solution may be 1 cP to 2000 cP and preferably 5 cP to 200cP, and in the case where the inkjet printing method is used, theviscosity of the decoloring solution may be 1 cP to 55 cP and preferably5 cP to 20 cP.

Meanwhile, in order to allow the viscosity of the decoloring solution tosatisfy the aforementioned range, it is preferable to use a method forfurther adding the viscosity agent. Therefore, the viscosity agentimproves the viscosity of the decoloring solution to help to suppressdiffusion of the solution and form the depolarization region having adesired size at a desired position. If the solution having the highviscosity is applied on the rapidly moving polarizer, since a relativespeed difference between a liquid and the polarizer, which is generatedwhen application is performed, is reduced, diffusion of the solutioninto an undesired portion is prevented, and fluidization of thesolution, which is applied for a time when decoloring is performed untilwashing after application, is reduced, and thus the depolarizationregion having a desired position or size may be formed.

The viscosity agent is not limited as long as the viscosity agent canhave low reactivity and increase the viscosity of the solution, but forexample, it is more preferable that the viscosity agent includes onekind or more selected from the group consisting of a polyvinylalcohol-based resin, a polyvinyl acetoacetate-based resin, anacetoacetyl group-denatured polyvinyl alcohol-based resin,butenediolvinyl alcohols, polyacrylamides, and polyethylene glycols.

Meanwhile, the viscosity agent may be included in the content of 0.5 wt% to 30 wt % and preferably 2.5 wt % to 15 wt %, based on the totalweight of the decoloring solution. In the case where the content of theviscosity agent is more than the aforementioned range, the viscosity isexcessively increased, and thus washing is not effectively performed,and in the case where the content of the viscosity agent is excessivelylow, the viscosity is low, and thus it is difficult to implement adecolored region having a desired shape and a desired size by diffusionand fluidization of the liquid.

Further, the depolarization region may have various shapes but is notlimited thereto, and the depolarization region may be formed at anyposition on the entire polarizing plate.

The depolarization region may be continuously formed in one region ofthe polarizer not requiring a polarizing effect. Specifically, thedepolarization region may be a region of the polarizer where a cameramodule is positioned.

Specifically, an area of at least one depolarization region may be 0.5mm² or more and 500 mm² or less.

In the case where the decoloring solution comes into contact with thepolarizer to form the depolarization region, distortion of an appearanceof the polarizer may be accompanied and this may be increased as thearea of the depolarization region is increased. Therefore, the presentinventors found a condition of the decoloring solution and a treatmentmethod thereof which may suppress surface wrinkles of the polarizeraccording to swelling of the polarizer to minimize a distortionphenomenon in the depolarization region even though one region of thepolarizer having the area of 0.5 mm² or more and 500 mm² or less isdepolarized by a chemical method.

Meanwhile, a depolarization mechanism through the depolarization step ofthe present invention will be specifically described below. It is knownthat a polyvinyl alcohol complex dyed with the iodine and/or dichromaticdyes may absorb light in a range of visible rays, such as the wavelengthband in a range of 400 nm to 800 nm. In this case, if the decoloringsolution comes into contact with the polarizer, the iodine and/ordichromatic dyes absorbing light having the visible-ray wavelength bandexisting in the polarizer are decomposed to decolor the polarizer andthus increase transmittance and reduce the polarization degree.

For example, in the case where the aqueous solution including potassiumhydroxide (KOH), which is the decolorant, comes into contact with someregions of the polyvinyl alcohol-based polarizer dyed with iodine, asindicated by the following Chemical Formulas 1 and 2, iodine isdecomposed by a series of processes. Meanwhile, in the case where aboric acid cross-linking process is performed when the polyvinylalcohol-based polarizer dyed with iodine is manufactured, as describedin the following Chemical Formula 3, potassium hydroxide directlydecomposes the boric acid to remove a cross-linking effect throughhydrogen bonding of polyvinyl alcohol and the boric acid.

12KOH+6I₂→2KIO₃+10KI+6H₂O  [Chemical Formula 1]

I₅ ⁻→IO₃ ⁻+6H⁻→3I₂+3H₂O

I₃ ⁻→I⁻+I₂  [Chemical Formula 2]

B(OH)₃+3KOH→K₃BO₃+3H₂O  [Chemical Formula 3]

That is, iodine and/or iodine ion complexes such as I₅ ⁻ (620 nm), I₃ ⁻(340 nm), and I₂ ⁻ (460 nm) absorbing light in the visible-ray regionare decomposed to generate I (300 nm or less) or a salt thereof, therebyallowing most of the light in the visible-ray region to penetrate.Accordingly, since the polarizer is depolarized in the region of 400 nmto 800 nm, which is the visible-ray region, transmittance is entirelyincreased to make the polarizer transparent. In other words, in order tomake polarization in the polarizer, arranged iodine complexes absorbingthe visible rays may be decomposed into a unimolecular form notabsorbing the visible rays, thereby performing depolarization.

It is preferable that the method for manufacturing the polarizing plateaccording to the present invention further includes, after thedepolarization step, performing washing by using alcohol or an acidsolution. This is because in the depolarization step, in the case wherea residual decoloring solution is not appropriately washed, the solutionis diffused or remains on the polarizer, and thus the depolarizationregion may be formed to have an undesired size and an undesired shapeand it is difficult to form the depolarization region having a minutesize.

Particularly, since it is easy to dry alcohol, alcohol can be easilyremoved, and alcohol does not affect transmittance or the polarizationdegree of the polarizer other than the depolarization region, and thusalcohol may be suitably used. For example, it is preferable that alcoholis ethanol, methanol, propanol, butanol, isopropyl alcohol, or a mixturethereof, but alcohol is not limited thereto. Further, in the case of theacid solution, the residual decolorant mainly having a basic property issubjected to a neutralization reaction with the acid solution to beremoved, and as the acid solution, for example, an acetic acid aqueoussolution, an adipic acid aqueous solution, a boric acid aqueoussolution, a phosphoric acid aqueous solution, a lactic acid aqueoussolution, a sulfuric acid aqueous solution, a nitric acid aqueoussolution, or a mixture solution thereof may be used, but the acidsolution is not limited thereto.

In the washing step, there is a method for immersing the polarizer inalcohol for 1 second to 180 seconds and more preferably 3 seconds to 30seconds, or applying alcohol or the acid solution on a local portiondecolored by contact with decoloring solution by using a dispenser,inkjet, or the like.

In the method for manufacturing the polarizing plate including thedepolarization region of the present invention, washing using alcohol orthe acid solution is performed after the decolorant is used, and thus,as described above, the iodine compound, the salt, and the like formedby the decolorant are washed out, and the content of iodine and iodineion complexes in the depolarization region is minimized. Accordingly,absorption of light by residual iodine and iodine ion complexes in thedepolarization region is reduced to secure an effect of making thepolarizer more transparent.

Further, the manufacturing method of the present invention may furtherinclude, not essentially but if necessary, after the forming of thedepolarization region, forming an optical layer on at least one surfaceof the polarizing plate. In this case, the optical layer may be apolymer film layer such as a protection film or a retardation film, afunctional film layer such as a luminance improvement film, or afunctional layer such as a hard coating layer, an antireflection layer,and a cohesive layer.

Meanwhile, the optical layer may be directly attached onto or formed onthe surface of the polyvinyl alcohol-based polarizer, or may be attachedonto the protection film or the other coating layer attached onto onesurface of the polyvinyl alcohol-based polarizer.

Next, a polarizing plate manufactured by using the method formanufacturing the polarizing plate according to the present inventionwill be described.

The polarizing plate according to the present invention includes: apolyvinyl alcohol-based polarizer dyed with at least one or more ofiodine and dichromatic dyes, and a protection film laminated on at leastone surface of the polyvinyl alcohol-based polarizer, in which thepolarizing plate locally has a depolarization region having singletransmittance of 80% or more at a wavelength band in a range of 400 nmto 800 nm, and arithmetic mean roughness (Ra) of the depolarizationregion is 100 nm or less.

In this case, the depolarization region of the polarizing plate, asdescribed above, refers to a region formed through a process of bringingthe decoloring solution into selective contact with some regions of thepolyvinyl alcohol-based polarizer dyed with the iodine and/ordichromatic dyes.

In the depolarization region, single transmittance at the wavelengthband in a range of 400 nm to 800 nm, which is the visible ray region,and preferably 450 nm to 750 nm is 80% or more and more preferably 90%or 92% or more. Further, the polarization degree of the depolarizationregion is 20% or less and more preferably 5% or less. As singletransmittance of the depolarization region is increased and thepolarization degree is decreased, visibility is improved, and thusperformance and image quality of the camera lens to be positioned in theaforementioned region may be further improved.

Further, single transmittance of the region of the polarizing plateother than the depolarization region is preferably 40% to 45% and morepreferably 42% to 45%. Moreover, the polarization degree of the regionof the polarizing plate other than the depolarization region ispreferably 99% or more. This is because the residual region other thanthe depolarization region should exhibit excellent optical propertieslike the aforementioned range by functioning as an original polarizingplate.

Meanwhile, in the polarizing plate according to the present invention,arithmetic mean roughness (Ra) of the depolarization region ispreferably 100 nm or less and more preferably 50 nm or less. Moreover,arithmetic mean roughness of the depolarization region of the polarizingplate according to the present invention may be 30 nm or less and morespecifically 20 nm or less.

Likewise, in the polarizing plate according to the present invention,root mean square roughness (Rq) of the depolarization region ispreferably 100 nm or less and more preferably 50 nm or less. Moreover,root mean square roughness of the depolarization region of thepolarizing plate according to the present invention may be 30 nm or lessand more specifically 20 nm or less.

In this case, the arithmetic mean roughness (Ra) in the presentinvention is a value regulated in JIS B0601-1994 and represents a valueobtained by sampling a reference length from a roughness curve in adirection of a mean line thereof and summating absolute values ofdeviations of the sampled portion from the mean line to the measuredcurve, followed by averaging, and the root mean square roughness (Rq) isregulated in JIS B0601-2001. The arithmetic mean roughness (Ra) and theroot mean square roughness (Rq) are measured by the optical profiler(Nanoview E1000, Nano System Inc.).

Generally, if roughness of the polarizer surface is increased, a haze isincreased by refraction and reflection of light. Therefore, the presentinvention exhibits a phenomenon where the haze is reduced due to areduction in roughness of the surface of the polarizer. In the casewhere roughness of the depolarization region satisfies theaforementioned range, the haze is sufficiently low, and vivid visibilitymay be secured. To be more specific, in the depolarization region of thepolarizing plate of the present invention, the haze is 3% or less andmore preferably 2% or less or 1% or less.

In the polarizer, an area of the depolarization region may be 0.5 mm² ormore and 500 mm² or less. Specifically, the polarizer according to thepresent invention is characterized in that the depolarization region isformed by using not the physical removing method but the chemicalmethod, and accordingly, a swelling phenomenon of the polarizer ismaximally suppressed to largely improve the surface wrinkles. Moreover,even though the area of the depolarization region of the polarizeraccording to the present invention is 0.5 mm² or more and 500 mm² orless, the surface wrinkles may be controlled not to affect performance.The surface wrinkles may be measured by surface roughness values such asthe arithmetic mean roughness (Ra) and the root mean square roughness(Rq). The aforementioned matters can be confirmed through 3D picturesand the surface roughness values of the depolarization regions of thepolarizers according to the following Examples and Comparative Examples.

Meanwhile, in the depolarization region, the content of the iodineand/or dichromatic dyes is 0.1 wt % to 0.5 wt % and preferably 0.1 wt %to 0.35 wt %. This is because, as described above, iodine existing in acomplex form on the polarizer is washed out by a reaction between thedecolorant and iodine, and thus the content of the iodine and/ordichromatic dyes is significantly reduced. In comparison with this, in aregion other than the depolarization region, the content of the iodineand/or dichromatic dyes is 1 wt % to 4 wt % and preferably 2 wt % to 4wt %.

In this case, the content of the iodine and/or dichromatic dyes wasmeasured by using an optical X-ray analytical device (manufactured byRigaku Electric Co., Ltd., trade name “ZSX Primus II”). In the presentinvention, average wt % per the volume of 19.2 mm³ was measured by usinga polarizer sheet-type sample having a size of 40 mm×40 mm and athickness of 12 μm.

The depolarization region, as described above, is formed through a stepof bringing the polarizer into contact with the decoloring solution. Inthis case, the content of the iodine and/or dichromatic dyes of thedepolarization region is significantly reduced as compared to the otherregion, and thus transmittance is largely improved.

Meanwhile, the polarizing plate of the present invention as describedabove may be attached to one surface or both surfaces of a display panelto be usefully applied to an image display. The display panel may be aliquid crystal panel, a plasma panel, and an organic light emittingpanel, accordingly, the image display may be a liquid crystal display(LCD), a plasma display panel (PDP), and an organic light emitting diode(OLED).

To be more specific, the image display may be a liquid crystal displayincluding a liquid crystal panel and polarizing plates provided on bothsurface of the liquid crystal panel, and in this case, at least one ofthe polarizing plates may be the polarizing plate including thepolarizer according to the present invention. That is, the polarizingplate is a polarizing plate including a polyvinyl alcohol-basedpolarizer dyed with iodine and/or dichromatic dyes, and a protectionfilm laminated on at least one surface of the polyvinyl alcohol-basedpolarizer, in which the polarizing plate locally has a depolarizationregion having single transmittance of 80% or more at a wavelength bandin a range of 400 nm to 800 nm and arithmetic mean roughness (Ra) of thedepolarization region is 100 nm or less.

In this case, a kind of liquid crystal panel included in the liquidcrystal display is not particularly limited. For example, all publiclyknown panels such as a passive matrix-type panel, such as a twistednematic (TN) type, a super twisted nematic (STN) type, a ferroelectic(F) type, or a polymer dispersed (PD) type; an active matrix-type panelsuch as a two terminal type or a three terminal type; and an in planeswitching (IPS) panel, and a vertical alignment (VA) panel, may beapplied, but the kind of liquid crystal panel is not limited thereto.Further, a kind of other constitutions constituting the liquid crystaldisplay, for example, upper and lower substrates (for example, a colorfilter substrate or an array substrate) and the like, is notparticularly limited, and a constitution publicly known in this fieldmay be adopted without a limit.

Meanwhile, the image display of the present invention includes otherparts such as a camera module, but is not limited thereto, and the otherparts such as the camera module may be positioned in the depolarizationregion. The camera module may be positioned in the depolarization regionwhere transmittance of the visible-ray region is improved and thepolarization degree is decreased, thereby achieving an effect ofincreasing visibility of a camera lens portion.

Hereinafter, the present invention will be described in more detailthrough the Examples. The following Examples are set forth to illustratethe present invention, but are not to be construed to limit the presentinvention.

Example 1

The polyvinyl alcohol-based film having the thickness of 60 μm (NipponGohsei Co., Ltd. M3000 grade) was subjected to the swelling process inthe pure solution at 25° C. for 15 seconds, and then subjected to thedyeing process in the iodine solution having the concentration of 0.2 wt% at 25° C. for 60 seconds. Thereafter, the polyvinyl alcohol-based filmwas subjected to the washing process in 1 wt % of the boric acidsolution at 45° C. for 30 seconds, and the six times elongation processwas then performed in 2.5 wt % of the boric acid solution at 52° C.After elongation, the polyvinyl alcohol-based film was subjected to thecomplementary color process in 5 wt % of KI solution, and then dried inthe oven at 60° C. for 5 minutes to manufacture the polarizer having thethickness of 22 μm.

Thereafter, the acryl-based protection film (thickness 40 μm) waslaminated on one surface of the manufactured polarizer by using thecation-based UV adhesive. Then, the decoloring solution (decolorant: KOH15%) was applied on the surface, on which the acryl-based protectionfilm was not laminated, by using the dispenser. Thereafter, after thetime of 35 seconds passed, washing was performed by using acetic acid(Daejung Chemicals & Metals Co., Ltd., 10 wt %, pH 2.4) as the acidsolution to manufacture the polarizer including the depolarizationregion.

Example 2

The polarizing plate including the depolarization region and having thepolarizer thickness of 12 μm was manufactured by the same method asExample 1, except that the polyvinyl alcohol-based film (Nippon GohseiCo., Ltd., M3000 grade) having the thickness of 30 μm was used.

Example 3

The polarizing plate including the depolarization region and having thepolarizer thickness of 8 μm was manufactured by the same method asExample 1, except that the polyvinyl alcohol-based film (Nippon GohseiCo., Ltd., M3000 grade) having the thickness of 20 μm was used.

Comparative Example 1

The polyvinyl alcohol-based film having the thickness of 60 μm (NipponGohsei Co., Ltd. M3000 grade) was subjected to the swelling process inthe pure solution at 25° C. for 15 seconds, and then subjected to thedyeing process in the iodine solution having the concentration of 0.2 wt% at 25° C. for 60 seconds. Thereafter, the polyvinyl alcohol-based filmwas subjected to the washing process in 1 wt % of the boric acidsolution at 45° C. for 30 seconds, and the six time elongation processwas then performed in 2.5 wt % of the boric acid solution at 52° C.After elongation, the polyvinyl alcohol-based film was subjected to thecomplementary color process in 5 wt % of KI solution, and then dried inthe oven at 60° C. for 5 minutes to manufacture the polarizer having thethickness of 22 μm.

The decoloring solution (decolorant: KOH 15%) was applied on one surfaceof the manufactured polarizer by using the dispenser. Thereafter, afterthe time of 35 seconds passed, washing was performed by using aceticacid (Daejung Chemicals & Metals Co., Ltd., 10 wt %, pH 2.4) as the acidsolution to manufacture the polarizer including the depolarizationregion.

Comparative Example 2

The polarizer including the depolarization region and having thethickness of 12 μm was manufactured by the same method as ComparativeExample 1, except that the polyvinyl alcohol-based film (Nippon GohseiCo., Ltd., M3000 grade) having the thickness of 30 μm was used.

Comparative Example 3

The polarizer including the depolarization region and having thethickness of 8 μm was manufactured by the same method as ComparativeExample 1, except that the polyvinyl alcohol-based film (Nippon GohseiCo., Ltd., M3000 grade) having the thickness of 20 μm was used.

Reference Example 1

The polyvinyl alcohol-based film having the thickness of 60 μm (NipponGohsei Co., Ltd. M3000 grade) was subjected to the swelling process inthe pure solution at 25° C. for 15 seconds, and then subjected to thedyeing process in the iodine solution having the concentration of 0.2 wt% at 25° C. for 60 seconds. Thereafter, the polyvinyl alcohol-based filmwas subjected to the washing process in 1 wt % of the boric acidsolution at 45° C. for 30 seconds, and the six times elongation processwas then performed in 2.5 wt % of the boric acid solution at 52° C.After elongation, the polyvinyl alcohol-based film was subjected to thecomplementary color process in 5 wt % of KI solution, and then dried inthe oven at 60° C. for 5 minutes to manufacture the polarizer notincluding the depolarization region and having the thickness of 22 μm.

Reference Example 2

The polarizer having the thickness of 12 μm was manufactured by the samemethod as Reference Example 1, except that the polyvinyl alcohol-basedfilm (Nippon Gohsei Co., Ltd., M3000 grade) having the thickness of 30μm was used.

Reference Example 3

The polarizer having the thickness of 8 μm was manufactured by the samemethod as Reference Example 1, except that the polyvinyl alcohol-basedfilm (Nippon Gohsei Co., Ltd., M3000 grade) having the thickness of 20μm was used.

Experimental Example 1—Evaluation of Optical Properties ofDepolarization Region

The polarizing plates manufactured by Examples 1 to 3 and the polarizersmanufactured by Comparative Examples 1 to 3 were cut to have the size of40 mm×40 mm, the specimen was fixed to the measurement holder, andinitial optical properties of the depolarization region, that is, singletransmittance and the polarization degree were measured by using theUV-VIS spectrometer (V-7100, manufactured by JASCO Corp.). Meanwhile,initial optical properties of the polarizers not having thedepolarization region, which were manufactured by Reference Examples 1to 3, were also measured. Particularly, the values at 550 nm aredescribed in Table 1.

Experimental Example 2—Measurement of Surface Roughness

In the polarizing plates manufactured by Examples 1 to 3 and thepolarizers manufactured by Comparative Examples 1 to 3, surfaceroughnesses of the depolarization regions having the same size weremeasured by using the optical profiler (Nanoview E1000, Nano SystemInc.) and the 20 magnification lens. Meanwhile, surface roughnesses ofthe polarizers not having the depolarization region, which weremanufactured by Reference Examples 1 to 3, were measured. The resultvalues are described in Table 1.

Experimental Example 3—Measurement of Haze

In the polarizing plates manufactured by Examples 1 to 3 and thepolarizers manufactured by Comparative Examples 1 to 3, hazes of thedepolarization regions having the same size were measured by using thehaze meter (NDH 500SP, NIPPON DENSHOKU INDUSTRIES). Meanwhile, the hazesof the polarizers not having the depolarization region, which weremanufactured by Reference Examples 1 to 3, were measured. The resultvalues are described in Table 1.

TABLE 1 Arithmetic Root mean Thickness mean square of SinglePolarization roughness roughness polarizer transmittance degree Haze(Ra) (Rq) Classification (μm) (%) (%) (%) (nm) (nm) Example 1 22 92.440.12 0.3 15 18 Example 2 12 92.35 0.19 0.3 8 11 Example 3 8 92.38 0.110.3 3 4 Comparative 22 92.31 0.13 3.6 270 340 Example 1 Comparative 1292.29 0.19 3.1 280 360 Example 2 Comparative 8 92.41 0.12 3.2 270 340Example 3 Reference 22 42.5 99.99 0.3 13 17 Example 1 Reference 12 42.599.99 0.3 5 9 Example 2 Reference 8 42.5 99.99 0.3 2 3 Example 3

Reviewing Examples 1 to 3 and Comparative Examples 1 to 3 of Table 1, itcould be confirmed that when depolarization was performed by using thedecoloring solution, in the case where the protection film was firstlaminated on one surface of the polarizer, the surface roughness and thehaze of the depolarization region were significantly small.

Further, reviewing FIG. 1 where the polarizing plate of the followingExample 1 was photographed, in the 3D picture of the depolarizationregion, it could be confirmed that the surface was very flat and surfaceroughness was uniform, but reviewing FIG. 2 where the polarizer ofComparative Example 1 was photographed, it could be confirmed that thewrinkles were formed on the surface of the depolarization region.

Meanwhile, reviewing Examples 1 to 3 and Reference Examples 1 to 3 ofTable 1, it could be confirmed that through the decoloring step, in thedepolarization region, single transmittance was largely improved to 92%or more and the polarization degree was reduced to 0.1% or less, andthus depolarization was implemented. Further, it could be confirmed thatlike Examples 1 to 3, in the case where the decoloring process wasperformed by forming the protection film on one surface, there was nolarge difference as compared to roughness of the region which was notdecolored.

Although the exemplary embodiments of the present invention aredescribed in detail, the scope of the present invention is not limitedto the exemplary embodiments, and it will be apparent to those skilledin the art that various modifications and changes may be made theretowithout departing from the technical spirit of the present inventiondescribed in the claims.

1-15. (canceled)
 16. A polarizing plate comprising: a polyvinylalcohol-based polarizer dyed with at least one or more of iodine anddichromatic dyes, and a protection film laminated on at least onesurface of the polyvinyl alcohol-based polarizer, wherein the polarizingplate locally has at least one depolarization region having singletransmittance of 80% or more at a wavelength band in a range of 400 nmto 800 nm, and arithmetic mean roughness (Ra) of the depolarizationregion is 100 nm or less.
 17. The polarizing plate of claim 16, whereinroot mean square roughness (Rq) of the depolarization region is 100 nmor less.
 18. The polarizing plate of claim 16, wherein an area of atleast one depolarization region is 0.5 mm² or more and 500 mm² or less.19. The polarizing plate of claim 16, wherein in the depolarizationregion of the polarizing plate, a polarization degree is 20% or less.20. The polarizing plate of claim 16, wherein in a region of thepolarizing plate other than the depolarization region, the singletransmittance is 40% to 45% and a polarization degree is 99% or more.21. The polarizing plate of claim 16, wherein in the depolarizationregion of the polarizing plate, a haze is 3% or less.
 22. The polarizingplate of claim 16, wherein in the depolarization region, a content of atleast one or more of the iodine and dichromatic dyes is 0.1 wt % to 0.5wt %, and in a region other than the depolarization region, the contentof at least one or more of the iodine and dichromatic dyes is 1 wt % to4 wt %.